Comparison of apical and basal surfaces of confluent endothelial cells: patch-clamp and viral studies

Treadmill running and Levisticum Officinale extract protect against LPS-induced memory deficits by modulating neurogenesis, neuroinflammation and oxidative stress

Neuroinflammation plays an essential role in the pathogenesis of Alzheimer's disease. The preventive effect of physical exercise on attenuating neuroinflammation has not been completely defined. Levisticum officinale is known as a medicinal plant with antioxidant and anti-inflammatory properties. The current study was designed to investigate the neuroprotective impacts of treadmill running and Levisticum officinale on lipopolysaccharide (LPS)-induced learning and memory impairments and neuroinflammation in rats. Male Wistar rats ran on a treadmill and/or were pretreated with Levisticum officinale extract at a dose of 100 mg/kg for a week. Then, rats received intraperitoneal injection of LPS at a dose of 1 mg/kg. Treadmill running and/or treatment of extract lasted three more weeks. Behavioral, molecular, biochemical and immunohistochemical assessments were carried out after the end of the experiment. LPS administration resulted in spatial learning and memory impairments along with increased mRNA expression of interleukin-6 and malondialdehyde levels, as well as decreased superoxide dismutase activity and neurogenesis in the hippocampus. Moreover, treadmill running for four weeks, alone and in combination with Levisticum officinale extract attenuated spatial learning and memory deficits, decreased the mRNA expression of interleukin-6 and malondialdehyde levels, and enhanced superoxide dismutase activity and neurogenesis in the hippocampus. In conclusion, the advantageous effects of running exercise and Levisticum officinale extract on LPS-induced memory impairments are possibly due to the antioxidant and anti-inflammatory activity and enhancing neurogenesis.

Neuroprotective effects of Levisticum officinale on LPS-induced spatial learning and memory impairments through neurotrophic, anti-inflammatory, and antioxidant properties

Levisticum officinale (Apiaceae) has been identified as a medicinal plant in traditional medicine, with the anti-inflammatory, antioxidant, and anticholinesterase activities. The present study aims to evaluate the effects of Levisticum officinale extract (LOE) on lipopolysaccharide (LPS)-induced learning and memory deficits and to examine its potential mechanisms. LOE was administered to adult male Wistar rats at doses of 100, 200, and 400 mg kg-1 for a week. Later, LPS was intraperitoneally injected at a dose of 1 mg kg-1 to induce neuroinflammation, and treatment with LOE continued for 3 more weeks. Behavioral, biochemical, and molecular analyses were performed at the end of the experiment. Moreover, quantitative immunohistochemical assessments of the expression of Ki-67 (intracellular proliferation marker) in the hippocampus were performed. The results revealed that LPS injection caused spatial memory impairment in the rats. Daily LOE treatment at applied doses for 4 weeks attenuated spatial learning and memory deficits in LPS-injected rats. Furthermore, LPS significantly increased the mRNA expression level of interleukin-6 in the hippocampus, which was accompanied by decreased brain-derived neurotrophic factor (BDNF) mRNA expression levels. Moreover, LPS increased the levels of malondialdehyde, reduced the antioxidant enzyme activities of catalase and superoxide dismutase in the hippocampus, and impaired neurogenesis. However, pre-treatment with LOE at a dose of 100 mg kg-1 significantly reversed the LPS-induced changes, and improved neurogenesis. In conclusion, the beneficial effect of LOE on the improvement of learning and memory could be attributed to its anti-inflammatory and antioxidant activities, along with its ability to increase BDNF expression and neurogenesis in the hippocampus.

Obesity is not a descriptive factor for oxidative stress and viscosity in follicular fluid of in vitro fertilization patients

BACKGROUND

Obesity's impact on micro-environmental oxidative stress and follicular fluid (FF) viscosity and whether or not it has any effect on in vitro fertilization (IVF) success is a matter of debate.

AIMS

In this study, our aim was to evaluate the levels of oxidative stress markers and the FF viscosity in obese and non-obese patients.

METHODS

Eighty norm-responder patients undergoing IVF were prospectively grouped according to their body mass indexes (BMI). Group 1 (n = 40) and group 2 (n = 40) had BMI values of ≤24.9 and ≥25.0, respectively. Total sulfhydryl (RSH) levels (nmol/m) and the formation of thiobarbituric acid-reactive substances (malondialdehyde, or MDA) (µmol/ml) in FFs were quantified. For the first time in our study, FF viscosity with changing BMI values was also determined.

RESULTS

The mean levels of MDA (µmol/ml) and RSH (nmol/ml) were not significantly different between groups (1.37 ± 0.51; 1.51 ± 0.51; p > 0.05 for MDA and 0.42 ± 0.30; 0.41 ± 0.20; p > 0.05 for RSH, respectively). Similarly, the FF viscosity (centipoise) was not different between groups (1.28 ± 0.28; 1.30 ± 0.19; p < 0.05, respectively). Independent of BMI, no correlation was found between FF levels of oxidative markers and the number of oocytes retrieved or the fertilization rates.

CONCLUSIONS

In our study, we found no difference in the levels of follicular oxidative and anti-oxidative markers or the follicular fluid viscosity with changing BMI values. We also demonstrated that the levels of oxidative stress markers and the viscosity of follicular fluid did not affect clinical outcomes.

Antidiabetic, antioxidant, and antilipid peroxidative activities of Dracocephalum polychaetum shoot extract in streptozotocin-induced diabetic rats: In vivo and in vitro studies

CONTEXT

Dracocephalum polychaetum Bornm. (Lamiaceae) is used in folk medicine and contains antioxidant agents.

OBJECTIVES

The objective of this study is to investigate the antidiabetic, antioxidant, and antilipid peroxidative properties of methanol extract of D. polychaetum aerial parts.

MATERIALS AND METHODS

The effect of extract (200, 300, and 400 mg/kg, b.w.) on oral glucose tolerance test (OGTT) was investigated. Also, extract (300 mg/kg) administered orally in diabetic rats for 14 d then, serum levels of some biochemical factors were evaluated. Pancreas samples were used for the determination of malondealdehyde (MDA) level, glutathione (GSH) content, superoxide dismutase, and catalase enzyme activities. Red blood cells (RBCs) and plasma were used for MDA estimation. Pancreatic α-amylase inhibition, DPPH (1,1-diphenyl-2-picrylhydrazyl), and FRAP (ferric reducing antioxidant power) assays were done. The total flavonoid content of the extract was determined by spectrophotometry.

RESULTS

Extract (300 mg/kg) decreased serum glucose level (27.1%) significantly at 120 min in OGTT. Serum levels of creatinine, triglycerides, cholesterol, alanine amino transferase and MDA levels in plasma, RBCs, and pancreas significantly decreased in treated (300 mg/kg) diabetic rats, while pancreatic GSH content, superoxide dismutase, and catalase enzymatic activities increased (p < 0.05). The IC50 values for the extract and butyl hydroxyanisole were 5.6 and 1.15 mg/mL in DPPH and 0.155 and 0.062 mg/mL in the FRAP methods, respectively. The extract had no inhibitory effect on α-amylase activity. The total amount of flavonoids of the extract was estimated to be 1.8% (g/g) on the basis of quercetin content.

CONCLUSION

Dracocephalum polychaetum shoot extract has antioxidant, antihyperlipidemic, and antilipid peroxidative properties.

Effects of curcumin on acute spinal cord ischemia-reperfusion injury in rabbits

Object

The object of this study was to conduct a prospective, randomized, laboratory investigation of the neuroprotective effects of curcumin functionally, biochemically, and histologically in an experimental acute spinal cord ischemia-reperfusion injury on rabbits.

Methods

Eighteen rabbits were randomly assigned to 1 of 3 groups: the sham group, the ischemia-reperfusion group, or the curcumin group. Spinal cord ischemia was induced by applying an infrarenal aortic cross-clamp for 30 minutes. At 48 hours after ischemia, neurological function was evaluated with modified Tarlov criteria. Biochemical changes in the spinal cord and plasma were observed by measuring levels of malondialdehyde (MDA), advanced oxidation protein products (AOPP), glutathione (GSH), superoxide dismutase (SOD), catalase (CAT), nitrite/nitrate, and tumor necrosis factor-α (TNF-α). Histological changes were examined with H & E staining. Immunohistochemical staining with antibodies against caspase-3 was performed to evaluate cell apoptosis after ischemia.

Results

In the curcumin group, neurological outcome scores were statistically significantly better compared with the ischemia-reperfusion group. In the ischemia-reperfusion group, MDA, AOPP, and nitrite/nitrate levels were significantly elevated in the spinal cord tissue and the plasma by the induction of ischemia-reperfusion. The curcumin treatment significantly prevented the ischemia-reperfusion–induced elevation of nitrite/nitrate and TNF-α. In addition, the spinal cord tissue and the plasma SOD, GSH, and CAT levels were found to be preserved in the curcumin group and not statistically different from those of the sham group. Histological evaluation of the tissues also demonstrated a decrease in axonal damage, neuronal degeneration, and glial cell infiltration after curcumin administration.

Conclusions

Although further studies including different dose regimens and time intervals are required, curcumin could attenuate a spinal cord ischemia-reperfusion injury in rabbits via reducing oxidative products and proinflammatory cytokines, as well as increasing activities of antioxidant enzymes and preventing apoptotic cell death.

The role of cyclooxygenase-derived oxidative stress in surgically induced lymphedema in a mouse tail model

CONTEXT

Oxidative stress may contribute to lymphedema and subsequent tissue damage. However, the causal role of oxidative stress in lymphedema remains unclear.

OBJECTIVE

We attempted to detect and identify the free radicals formed in lymphedema fluid and assessed the protective mechanisms and effects of specific enzyme inhibitors and natural antioxidants.

MATERIALS AND METHODS

To study the level of postsurgical oxidative stress with lymphedema in a mouse tail model, we used an electron spin resonance (ESR) method and an ascorbyl radical's ESR spectrum as an oxidative stress biomarker. The drug-treatment group received an i.p. injection with indomethacin (2 mg/kg), baicalein (15 mg/kg), MK-886 (3 mg/kg), zileuton (6.25 mg/kg), diphenyleneiodonium (DPI; 1 mg/kg), sulforaphane (30 mg/kg), oryzanol (30 mg/kg) or sesamol (30 mg/kg) once daily for 14 d from the day of operation. All animals were sacrificed on day 14.

RESULTS

Administration of indomethacin, sulforaphane, oryzanol and sesamol significantly suppressed both the tail volume (56.9%, 77.8%, 72.2% and 38.1% inhibition, respectively, p < 0.01) and ascorbyl radical signals (31.4%, 54.5%, 79.3% and 57.1% inhibition, respectively, p < 0.01), compared with the control mice. No significant differences were found between any of the baicalein, MK-886, or zileuton groups compared with the control. DPI suppressed the tail volume (25.9% inhibition, p < 0.01) but not the ascorbyl radical signals.

CONCLUSION

This study showed that COX-derived oxidative stress plays a major role in the pathological mechanisms of surgically induced lymphedema. Indomethacin, sulforaphane, oryzanol and sesamol exhibit potent protective properties against surgically induced lymphedema.

Neuroprotective effects of gabapentin on spinal cord ischemia-reperfusion injury in rabbits

Object

Extensive research has been focused on neuroprotection after spinal cord trauma to alleviate the effects of secondary injury. This study aims to investigate the neuroprotective effects of gabapentin in an experimental spinal cord ischemia reperfusion injury.

Methods

Thirty-two adult male New Zealand white rabbits received spinal cord ischemic injury using the aortic occlusion model. Animals were divided into 4 groups (sham, control, low-dose, and high-dose treatment groups; 8 rabbits in each group). High (200 mg/kg) and low (30 mg/kg) doses of gabapentin were administered to the animals in the treatment groups after spinal cord ischemic injury. Neurological status of the animals, ultrastructural findings in injured tissue samples, and levels of tissue injury markers in these 2 groups were compared with findings in the animals that did not receive the ischemic procedure (sham-operated group) and those that received normal saline after administration of ischemia.

Results

Regarding levels of tissue injury marker levels after ischemic injury, animals in the gabapentin-treated groups demonstrated better results than animals in the other groups. The ultrastructural findings and caspase-3 activity were similar. The treatment groups demonstrated better results than the other groups.

Conclusions

Gabapentin demonstrated significant neuroprotection after early phases of ischemic injury. Further studies with different experimental settings including neurological outcome are required to achieve conclusive results.

Membrane potential depolarization decreases the stiffness of vascular endothelial cells

The stiffness of vascular endothelial cells is crucial to mechanically withstand blood flow and, at the same time, to control deformation-dependent nitric oxide release. However, the regulation of mechanical stiffness is not yet understood. There is evidence that a possible regulator is the electrical plasma membrane potential difference. Using a novel technique that combines fluorescence-based membrane potential recordings with atomic force microscopy (AFM)-based stiffness measurements, the present study shows that membrane depolarization is associated with a decrease in the stiffness of endothelial cells. Three different depolarization protocols were applied, all of which led to a similar and significant decrease in cell stiffness, independently of changes in cell volume. Moreover, experiments using the actin-destabilizing agent cytochalasin D indicated that depolarization acts by affecting the cortical actin cytoskeleton. A model is proposed whereby a change of the electrical field across the plasma membrane is directly sensed by the submembranous actin network, regulating the actin polymerization:depolymerization ratio and thus cell stiffness. This depolarization-induced decrease in the stiffness of endothelial cells could play a role in flow-mediated nitric-oxide-dependent vasodilation.

The involvement of nitric oxide and endothelin-1 in exercise-induced bronchospasm in young soccer players

OBJECTIVES

To investigate the levels of nitric oxide (NO) and endothelin-1 (ET-1) in soccer players with exercise-induced bronchospasm (EIB), to test whether these endogenous vasoactive molecules are involved in the development of EIB, and to examine the possible participation of reactive oxygen metabolites in these alterations.

DESIGN

Observational study.

SETTING

Football club.

PARTICIPANTS

Forty-three soccer players (N = 43) aged 16 to 22 years performed maximal exercise test on a treadmill by using Bruce protocol.

INTERVENTIONS

Respiratory function tests were evaluated before and after exercise tests. Participants were grouped as control (n = 35) or EIB (n = 8) groups according to the respiratory function test results.

MAIN OUTCOME MEASURES

Endothelin-1 (ET-1), nitric oxide (NO), carbonyl, malondialdehyde, and glutathione levels were determined from the blood samples taken before and after exercise tests.

RESULTS

In the control group, significant decreases in plasma ET-1 and serum NO levels were determined after exercise. On the other hand, plasma malondialdehyde and carbonyl levels were significantly decreased, whereas glutathione levels were significantly increased after exercise. In the EIB group, blood levels of NO, ET-1, carbonyl, and malondialdehyde after exercise were found to be significantly increased compared with pre-exercise levels.

CONCLUSIONS

These findings demonstrate that in young soccer players, EIB is associated with elevated serum NO and plasma ET-1 levels. Moreover, significant increases in lipid peroxidation and protein oxidation and decreases in antioxidant sulfhydryl (RSH) content indicate a significant compromise in the blood antioxidant status and the presence of systemic oxidative stress in young athletes with EIB.

Anti-apoptotic and neuroprotective effects of α-lipoic acid on spinal cord ischemia-reperfusion injury in rabbits

PURPOSE

Radical oxygen species produced after injury counteracts antioxidant activity and frequently causes severe oxidative stress for the tissues. Alpha-lipoic acid is a powerful metabolic antioxidant with immunomodulatory effects which provides neuroprotection. The aim of this study is to investigate the neuroprotective and anti-apoptotic effects of alpha-lipoic acid on spinal cord ischemia-reperfusion.

METHODS

Twenty-four adult, male, New Zealand rabbits were divided into sham (n = 8), control (n = 8), and treatment groups (n = 8). The abdominal aorta was clamped for 30 min by an aneurysm clip, approximately 1 cm below the renal artery and 1 cm above the iliac bifurcation in control and treatment groups. Only laparotomy was performed in the sham group. Twenty-five cubic centimeters of saline in control group and 100 mg/kg lipoic acid were administered intraperitoneally in the treatment group after closure of the incision. The animals were killed 48 h later. Spinal cord segments between L2 and S1 were harvested for analysis. Levels of nitric oxide, glutathione, malondialdehyde, advanced oxidation protein products, and superoxide dismutase were analyzed as markers of oxidative stress and inflammation. Caspase-3 activity was analyzed to detect the effect of lipoic acid on apoptosis.

RESULTS

In all measured parameters of oxidative stress, administration of lipoic acid significantly demonstrated favorable effects. Both plasma and tissue levels of nitric oxide, glutathione, malondialdehyde, and advanced oxidation protein products significantly changed in favor of antioxidant activity. There was no significant difference between the plasma superoxide dismutase levels of the groups. Histopathological evaluation of the tissues also demonstrated significant decrease in cellular degeneration and infiltration parameters after lipoic acid administration. However, lipoic acid has no effect on caspase-3 activity.

CONCLUSIONS

Although further studies considering different dose regimens and time intervals are required, the results of the present study prove that alpha-lipoic acid has favorable effects on experimental spinal cord ischemia-reperfusion injury.

The evaluation of the oxidative stress parameters in nondiabetic and diabetic senile cataract patients

The aim of the present study was to evaluate the copper (Cu), zinc (Zn), malondialdehyde (MDA), glutathione (GSH), and advanced oxidation protein products (AOPP) levels and superoxide dismutase (SOD) activities in diabetic senile cataract. Ten patients with diabetic senile cataract and ten patients with nondiabetic senile cataract (control group) were included in this study. AOPP, MDA, and GSH levels and SOD activity were measured by a spectrophotometric method. Serum, lens Cu, and Zn levels were measured by an atomic absorption spectrophotometric method. Both the lens and serum Zn and Cu levels between the two groups were not significantly different (p > 0.05). GSH, AOPP, and MDA levels and the SOD activities in the diabetic senile cataract group were significantly increased as compared to the control group (p < 0.05). Oxidative stress is one of the major factors which may lead to the early cataract formation. Oxidative events are of great importance in diabetic complications and, particularly in the lens, may have a role in the pathogenesis of cataract associated with diabetes mellitus as exhibited in this study.

Microsomal Prostaglandin Synthase-1–Derived Prostaglandin E 2 Protects Against Angiotensin II–Induced Hypertension via Inhibition of Oxidative Stress

Prostaglandin (PG) E 2 has an established role in the regulation of vascular tone and reactivity. The present study examined the role and mechanism of microsomal PG synthase-1 (mPGES-1) in vascular response to angiotensin II (Ang II) infusion. A 7-day Ang II infusion at 0.35 mg/kg per day via osmotic minipump had no obvious effect on mean arterial blood pressure in mPGES-1 +/+ mice but induced a marked hypertensive response in mPGES-1 −/− mice, associated with a parallel increase in urinary 8-isoprostane excretion and aortic NADPH oxidase activity and mRNA expression of p47 phox , gp91 phox , and Nox1. The hypertension in mPGES-1 −/− mice was completely prevented by Tempol treatment and was fully restored on termination of the antioxidant. Apocynin induced a similar blood pressure–lowering effect as Tempol. The Ang II infusion induced mRNA expression of mPGES-1, as well as mPGES-2 and cytosolic PGE synthase in the aortas as assessed by real-time RT-PCR. Immunohistochemistry revealed remarkably enhanced immunoreactivity of mPGES-1 mostly in vascular smooth muscle cells. In cultured vascular smooth muscle cells, Ang II exerted a direct stimulatory effect on reactive oxygen species production, NADPH oxidase activity, and expression of p47 phox , gp91 phox , and Nox1 that were all inhibited by PGE 2 . The −/− mice also exhibited enhanced renal hemodynamic response to acute Ang II infusion at 150 nmol/kg per minute via a jugular vein over a period of 40 minutes. These results suggest that mPGES-1–derived PGE 2 buffers Ang II–induced vasoconstriction via inhibition of NADPH oxidase–dependent reactive oxygen species production.

Antihypertensive effects of selective prostaglandin E2 receptor subtype 1 targeting

Clinical use of prostaglandin synthase-inhibiting NSAIDs is associated with the development of hypertension; however, the cardiovascular effects of antagonists for individual prostaglandin receptors remain uncharacterized. The present studies were aimed at elucidating the role of prostaglandin E2 (PGE2) E-prostanoid receptor subtype 1 (EP1) in regulating blood pressure. Oral administration of the EP1 receptor antagonist SC51322 reduced blood pressure in spontaneously hypertensive rats. To define whether this antihypertensive effect was caused by EP1 receptor inhibition, an EP1-null mouse was generated using a "hit-and-run" strategy that disrupted the gene encoding EP1 but spared expression of protein kinase N (PKN) encoded at the EP1 locus on the antiparallel DNA strand. Selective genetic disruption of the EP1 receptor blunted the acute pressor response to Ang II and reduced chronic Ang II-driven hypertension. SC51322 blunted the constricting effect of Ang II on in vitro-perfused preglomerular renal arterioles and mesenteric arteriolar rings. Similarly, the pressor response to EP1-selective agonists sulprostone and 17-phenyltrinor PGE2 were blunted by SC51322 and in EP1-null mice. These data support the possibility of targeting the EP1 receptor for antihypertensive therapy.

The effect of vaginal candidiasis on the levels of the oxidative biomarkers in plasma and tissue samples of diabetic rats

The aim of this study is to determine the relation between diabetes and vaginal candidiasis in terms of oxidative biomarker levels in a vaginal candidiasis model of the diabetic rats by evaluating malondialdehyde (MDA), sulphydrile groups or glutathione (RSH), and ascorbic acid (C vit) levels. All rats were randomly divided into five groups. All of the groups were observed for 21 days. In the treated diabetes groups, MDA (0.90, 0.68 nmol/ml and 3.78, 3.79 nmol/g tissue, plasma and vaginal tissue, respectively) and RSH (227, 171 nmol/100 ml 0.38, 0.37 micromol/g tissue, plasma and vaginal tissue, respectively) levels were found to be decreased while the levels of C vit were found to be increased (0.49, 0.37 micromol/l 2.39, 2.01 nmol/g tissue plasma, and vaginal tissue, respectively) (P < 0.05). In the groups of untreated diabetes, vaginal candidiasis were found to be more serious and oxidative biomarkers were found to be increased (MDA 1.30, 1.26 nmol/ml and 7.82, 2.37 nmol/g tissue and RSH 258, 145 nmol/100 ml and 0.31, 0.46 micromol/g tissue) while the antioxidant C vit levels were found to be decreased (0.24, 0.17 micromol/l 1.33, 2.66 nmol/g tissue) (P < 0.05). RSH, plasma MDA, blood glucose, and tissue MDA levels of vaginal candidiasis embedeled diabetic rats, were found to be higher than those in untreated diabetic and untreated vaginitis enbedeled rats 'P < 0.05'. Vaginal candidiasis caused oxidative stress in diabetic rats working together. Systemic oxidative stress biomarkers were found to be affected from vaginal candidiasis although it was a local mucosal infection.

Low-intensity ultraviolet A irradiation of the lens capsule to remove lens epithelial cells during cataract surgery

PURPOSE

To assess the effectiveness and safety of low-intensity ultraviolet A (UVA) irradiation in removing lens epithelial cells (LECs) during cataract surgery and compare them with those of mechanical polishing and no treatment.

SETTING

Eyecove Ophthalmology Clinics, Pune, India.

METHODS

This prospective randomized double-masked study consisted of preoperative screening of 36 patients, of which 30 met the inclusion criteria and were recruited. The patients had routine cataract surgery. A bean-shaped capsulorhexis was performed. After the nucleus and cortex were removed, the capsular bag was irradiated from inside with low-intensity UVA in 1 group. A second group had mechanical polishing, and a third group was not treated. A small flap of the anterior capsule was removed in each patient. The flap was stained and mounted in a Fuchs-Rosenthal chamber. For estimation of effectiveness, the area of capsule covered with epithelial cells was estimated by examination under a light microscope. One day postoperatively, an examination was performed to assess the safety of each technique.

RESULTS

The area of the capsule from which the LECs were removed was significantly larger in the UVA-irradiation group than in the mechanical-polishing group (P = .001) and the no-treatment group (P = .001). There was no significant difference between the mechanical-polishing and no-treatment groups (P>.05). The area of the capsule flap that was covered with LECs was significantly less in the UVA-irradiation group than in the mechanical-polishing group (P = .017) and the no-treatment group (P = .001). The mechanical-polishing group and no-treatment group were not significantly different from each other (P>.05). Corneal edema was significantly less in the UVA-irradiation group than in the mechanical-polishing group (P<.001) and no-treatment group (P = .012). No patient in the UVA-irradiation group had postoperative lid edema; 8 patients in each of the other 2 groups had lid edema. The difference was statistically significant (P<.0001). Pupil size was significantly larger in the UVA-irradiation group than in the mechanical-polishing group and no-treatment group; the difference was significant (both P = .0001). There was no significant difference in pupil size in the mechanical-polishing group and no-treatment group. No significant difference was observed between the 3 groups in visual acuity, conjunctival edema, anterior chamber flare, and intraocular pressure.

CONCLUSION

Ultraviolet A irradiation of the capsular bag was effective and safe in removing LECs from the anterior capsule during cataract surgery.

Antioxidant enzymes and diabetic retinopathy

The aim of this study was to discuss the serum copper (Cu), zinc (Zn), nitric oxide (NO), glutathione (GSH), advanced oxidation protein products (AOPP) levels, and superoxide dismutase (SOD) activities with diabetic retinopathy severity. Twenty-five patients with proliferative diabetic retinopathy (PDR group 1), 25 patients with nonproliferative diabetic retinopathy (NPDR group 2), and 25 nondiabetic controls (control group) were included in the study. Patients who had macrovascular complications of diabetes (coronary arterial disease, periferic vascular disease) were excluded. The major finding of our study was that we did not observe any differences between group 1 and 2, which we aimed to discuss the severity of diabetic retinopathy. As the levels of SOD and Zn were not different between the groups, statistically significant differences were observed for GSH, NO, and Cu levels when compared to control group. AOPP levels were statistically increased in group 1 compared to control group. It can be suggested that hyperglycemia in DM is associated with accelerated nonenzymatic glycation and oxidative stress.

Effects of leptin on oxidative stress in healthy and Streptozotocin-induced diabetic rats

AIMS/HYPOTHESIS

It is generally accepted that oxidative stress is responsible for etiology and complications of diabetes. During uncontrolled Type 1 diabetes, plasma leptin levels rapidly fall. However, it is not known whether diabetes-induced hypoleptinemia has any role in oxidative stress related to uncontrolled Type I diabetes. The present study was designed to examine the effects of leptin treatment on plasma lipid peroxidation and reduced glutathion of normal and streptozotocin(STZ)-induced diabetic rats.

METHODS

Diabetes was induced by single injection of Streptozotocin (55 mg/kg bw). One week after induction of diabetes, rats began 5-day treatment protocol of leptin injections of (0.1 mg/kg bw i.p.) or same volume vehicle. At the end of the 5th day, rats were sacrificed by cardiac puncture under anesthesia and their plasma was taken for plasma leptin, malondialdehyde, and reduced glutathione measurements.

RESULTS

Plasma leptin levels decreased in STZ-induced diabetic rats while plasma glucose, TBARS, and GSH levels increased. Plasma leptin levels were not affected with leptin treatment in both diabetic and non-diabetic rats. The elevation in plasma TBARS associated with STZ diabetes decreased with leptin treatment. Leptin also increased plasma GSH levels in diabetic rats. In non-diabetic rats, treatment with leptin did not change plasma TBARS and GSH levels.

CONCLUSIONS/INTERPRETATIONS

In conclusion, leptin treatment is able to attenuate lipid peroxidation in STZ-diabetic rats, in the onset of diabetes, by increasing the GSH levels without affecting hyperglycemia and hypoleptinemia.

Role of the nitric oxide pathway in ischemia-reperfusion injury in isolated perfused guinea pig lungs

We examined the role of the nitric oxide (NO) pathway on ischemia-reperfusion injury via the use of isolated perfused guinea pig lungs. We administered both L-Arginine and N-nitro-L-arginine methyl ester (L-NAME) to the lungs in or after 3 h of ischemia. We observed pulmonary artery pressures as well as tissue and perfusate malondialdehyde (MDA) and glutathione (GSH) levels. We observed that L-NAME significantly increased both tissue and perfusate GSH levels and pulmonary artery pressures, but it decreased both tissue and perfusate MDA levels. On the other hand, L-arginine significantly decreased pulmonary artery pressure and both tissue and perfusate glutathione levels, but it increased both tissue and perfusate MDA levels. Electron microscopic evaluation supported our findings by indicating the preservation of lamellar bodies of type II pneumocytes. We concluded that L-NAME administration during reperfusion improves lung recovery from ischemic injury.

Effects of melatonin in reducing the toxic effects of doxorubicin

Anthracycline antibiotics, such as doxorubicin and daunorubicin, constitute a group of wide spectrum therapeutic agents. Application of these drugs in chemotherapy is limited because of their toxic effects. Melatonin, the main secretory product of pineal gland, was recently found as a free radical scavenger and antioxidant. We decided to evaluate the tissue protective effect of melatonin against toxic effects of doxorubicin in six groups of rats. Rats were given doxorubicin (Dx) (45 mg/kg dose), melatonin (MEL) (10 mg/kg), first doxorubicin and then melatonin (DM), first melatonin and then doxorubicin (MD). The degree of kidney, lung, liver and brain cells' alterations were examined biochemically. In doxorubicin-treated group, malondialdehyde (MDA) levels of kidney, lung, liver and brain tissues were significantly increased but glutathione (GSH) levels were decreased compared to control rats. In the group in which first doxorubicin and then melatonin were given, MDA levels were significantly decreased compared to the doxorubicin-treated group. In doxorubicin-treated group, serum levels of creatinine, uric acid, blood urea nitrogen (BUN), Gamma-glutamyl transpeptidase (GGT) and Lactic acid dehydrogenase (LDH) were significantly increased while serum albumin and total protein levels were significantly decreased compared to control rats. Melatonin decreased the intensity of the changes produced by the administration of doxorubicin alone. Melatonin was quite efficient in reducing the formation of lipid peroxidation, restoring the tissue GSH contents and alterations of serum levels.

Prevention of doxorubicin-induced cardiotoxicity by melatonin

Anthracyclines, such as doxorubicin and daunorubicin, are highly effective anticancer agents. Cardiotoxicity made by these agents develops as a complication of the cancer chemotherapy. Melatonin, the chief secretory product of the pineal gland, was recently found to be a free radical scavenger and antioxidant. We decided to evaluate the tissue-protective effect of melatonin against myocardial toxic effects of doxorubicin in six groups of rats. Rats were given doxorubicin (Dx) (45 mg/kg dose) and melatonin (MEL) (10 mg/kg), first doxorubicin and then melatonin (DM), first melatonin and then doxorubicin (MD). The degree of cardiac muscle cell alterations were examined either histologically (mean total score technique) or biochemically. In doxorubicin-treated group, malondialdehyde (MDA) levels of the heart tissue were significantly increased, glutathione (GSH) levels were decreased compared to the control rats. In the group in which first doxorubicin and then melatonin was given, MDA levels were significantly decreased and glutathione (GSH) levels were increased compared to the doxorubicin-treated group. During ultrastructural analysis, in doxorubicin-treated group, cellular edema, mitochondrial deformation, decreased glycogen stores, and disordered myofibrillary structure were observed. In contrast, in first doxorubicin and then melatonin-treated group, normal cellular structure was observed. But, first melatonin and then doxorubicin-treated group was not significantly preserved from the doxorubicin-induced changes. By preventing lipid peroxidation and myocardial lesions, melatonin may be highly effective in protecting against doxorubicin-induced cardiotoxicity.

The effects of vitamin C supplementation on oxidative stress and antioxidant content in the brains of chronically exercised rats

The purpose of this study was to ascertain whether vitamin C supplementation during chronic exercise training alters rat brain antioxidant content. Female Wistar albino rats were exercised on a treadmill for 30 min/day for 6.5 weeks and were administered daily intraperitoneal injections of vitamin C (20 mg/kg). After the training period, chronically exercised rats showed no significant changes in total brain thiobarbituric acid reactive substances (TBARS) levels. In contrast, rats supplemented with vitamin C during the training period showed significantly elevated brain TBARS levels. If such results were extrapolated to man, where vitamin supplementation is a common practice, this would indicate that vitamin C supplementation may not protect brain tissue against exercise-induced oxidative damage, in such circumstances, this water-soluble antioxidant behaves as a pro-oxidant.

Increased nitric oxide is accompanied by lipid oxidation in adolescent varicocele

Summary One of the mechanisms of injury in varicocele has been proposed to be elevated nitric oxide (NO). We aimed to determine the association between the elevation of NO and lipid oxidation in varicocele compared with peripheral venous levels of these two substances as it has not been studied before. The study group consisted of 13 adolescents with left idiopathic varicocele of grades II-III. Blood specimens were obtained from dilated spermatic and peripheral veins simultaneously. Peripheral samples were also collected from 13 healthy children as controls. Nitrite/nitrate levels (NO(x)) and levels of malonedialdehyde (MDA) were determined using Griess reaction and thiobarbituric acid test, respectively. Results were compared with Kruskal-Wallis and Mann-Whitney tests. Peripheral NO(x) and MDA were the same in the study and control groups (p = 0.069 and p = 0.27, respectively). Spermatic vein NO(x) and MDA levels were elevated significantly compared with the peripheral levels in the study group (p = 0.005 and p = 0.048, respectively). Increased NO(x) levels with lipid oxidation occur locally in adolescent varicocele, implying that these events could be reversed by early treatment.

Potassium Channels and Membrane Potential in the Modulation of Intracellular Calcium in Vascular Endothelial Cells

The endothelium plays a vital role in the control of vascular functions, including modulation of tone; permeability and barrier properties; platelet adhesion and aggregation; and secretion of paracrine factors. Critical signaling events in many of these functions involve an increase in intracellular free Ca(2+) concentration ([Ca(2+)](i)). This rise in [Ca(2+)](i) occurs via an interplay between several mechanisms, including release from intracellular stores, entry from the extracellular space through store depletion and second messenger-mediated processes, and the establishment of a favorable electrochemical gradient. The focus of this review centers on the role of potassium channels and membrane potential in the creation of a favorable electrochemical gradient for Ca(2+) entry. In addition, evidence is examined for the existence of various classes of potassium channels and the possible influence of regional variation in expression and experimental conditions.

The effects of losartan and enalapril therapies on the levels of nitric oxide, malondialdehyde, and glutathione in patients with essential hypertension

Several recent studies have shown that essential hypertension is associated with increased oxidative stress, which may cause hypertension via enhanced oxidation and inactivation of nitric oxide. In this study, we investigated the malondialdehyde, nitric oxide, and glutathione levels in newly diagnosed essential hypertensive patients and whether or not there was any effect of antihypertensive treatment with angiotensin II type 1 receptor antagonist, losartan or angiotensin converting enzyme inhibitor, enalapril on plasma malondialdehyde, nitric oxide, and glutathione values. We selected 17 patients (F/M: 10/7, mean age: 46.12 +/- 9.2 years) for enalapril therapy (10-20 mg/d) and 14 patients (F/M: 8/6, mean age: 47.7 +/- 7.5 years) for losartan therapy (50-100 mg/d), and compared them with 12 normotensive controls. At the beginning of the study, both treated groups showed significantly higher plasma malondialdehyde and lower glutathione and nitric oxide in exhaled air compared to the control group. After 9 weeks of enalapril and losartan treatment, both systolic and diastolic pressure were significantly reduced. Both enalapril and losartan produced a significant decrease in plasma malondialdehyde and a significant increase in plasma glutathione levels and nitric oxide in exhaled air after 9 weeks. Initial values of plasma nitrate levels in patient groups were similar to the control group and increased significantly after the treatment period. In conclusion, both losartan and enalapril may be regulators between oxidant stress and the antioxidant system.

Clustering of very late antigen-4 integrins modulates K(+) currents to alter Ca(2+)-mediated monocyte function

Endothelial cell vascular cell adhesion molecule-1 (VCAM-1) activates adherent monocytes by clustering their very late antigen-4 (VLA-4) receptors, resulting in the modulation of the inwardly rectifying (I(ir)) and delayed rectifying (I(dr)) K(+) currents, hyperpolarization of the cells, and enhanced Ca(2+) influx (Colden-Stanfield M and Gallin EK. Am J Physiol Cell Physiol 275: C267-C277, 1998; Colden-Stanfield M and Scanlon M. Am J Physiol Cell Physiol 279: C488-C494, 2000). The present study was undertaken to test the hypothesis that monoclonal antibodies (MAbs) against VLA-4 (MAbVLA-4) mimic VCAM-1 to cluster VLA-4 integrins, which play a key role in signaling an increase in the secretion of the proinflammatory cytokine interleukin-8 (IL-8). Whole cell ionic currents and IL-8 secretion from THP-1 monocytes that were incubated on polystyrene, VCAM-1-immobilized MAbVLA-4 or an isotype-matched MAb against CD45 (MAbCD45) were measured. Clustering of VLA-4 integrins with a cross-linked MAbVLA-4, but not a monovalent MAbVLA-4, modulated the K(+) currents in an identical manner to incubation of cells on VCAM-1. Similarly, cross-linked MAbVLA-4 or VCAM-1 augmented Ca(2+)-mediated IL-8 secretion from THP-1 monocytes and was completely abolished by exposure to CsCl, an I(ir) blocker. Thus VLA-4 integrin clustering by cross-linked MAbVLA-4 mimics VCAM-1/VLA-4 interactions sufficiently to be associated with events leading to monocyte differentiation, enhanced Ca(2+)-mediated macrophage function, and possibly atherosclerotic plaque formation.

Ion channels and their functional role in vascular endothelium

Endothelial cells (EC) form a unique signal-transducing surface in the vascular system. The abundance of ion channels in the plasma membrane of these nonexcitable cells has raised questions about their functional role. This review presents evidence for the involvement of ion channels in endothelial cell functions controlled by intracellular Ca(2+) signals, such as the production and release of many vasoactive factors, e.g., nitric oxide and PGI(2). In addition, ion channels may be involved in the regulation of the traffic of macromolecules by endocytosis, transcytosis, the biosynthetic-secretory pathway, and exocytosis, e.g., tissue factor pathway inhibitor, von Willebrand factor, and tissue plasminogen activator. Ion channels are also involved in controlling intercellular permeability, EC proliferation, and angiogenesis. These functions are supported or triggered via ion channels, which either provide Ca(2+)-entry pathways or stabilize the driving force for Ca(2+) influx through these pathways. These Ca(2+)-entry pathways comprise agonist-activated nonselective Ca(2+)-permeable cation channels, cyclic nucleotide-activated nonselective cation channels, and store-operated Ca(2+) channels or capacitative Ca(2+) entry. At least some of these channels appear to be expressed by genes of the trp family. The driving force for Ca(2+) entry is mainly controlled by large-conductance Ca(2+)-dependent BK(Ca) channels (slo), inwardly rectifying K(+) channels (Kir2.1), and at least two types of Cl( -) channels, i.e., the Ca(2+)-activated Cl(-) channel and the housekeeping, volume-regulated anion channel (VRAC). In addition to their essential function in Ca(2+) signaling, VRAC channels are multifunctional, operate as a transport pathway for amino acids and organic osmolytes, and are possibly involved in endothelial cell proliferation and angiogenesis. Finally, we have also highlighted the role of ion channels as mechanosensors in EC. Plasmalemmal ion channels may signal rapid changes in hemodynamic forces, such as shear stress and biaxial tensile stress, but also changes in cell shape and cell volume to the cytoskeleton and the intracellular machinery for metabolite traffic and gene expression.

Effect of G-CSF on ethanol-induced hemorrhagic gastritis model in diabetes mellitus-induced rats

Diabetes mellitus can affect every organ system, including large and small vessels, eyes, nerves, kidneys and gastrointestinal system. Acid peptic disease is an inflammatory condition involving the upper gastrointestinal tract. The elevated serum glucose levels of diabetics affect traditional host defenses such as neutrophil counts and functions. We aimed to investigate changes of gastric mucosa and the role of impaired neutrophil functions in a diabetes-induced experimental model and whether G-CSF, which modulates neutrophil counts and function, has protective effects against gastric mucosal injury in diabetic rats. Fifty rats were divided into three groups. Diabetes mellitus was induced by a single dose of streptozotocin in 40 of 50 rats. Controls had a sham injection. The gastric mucosal lesions were produced by intragastric administration of 1 ml of 95% ethanol in all three groups. Granulocyte colony-stimulating factor (G-CSF) was subcutaneously injected to twenty of diabetes-induced rats. Stomach histology and tissue malondialdehyde and glutathione levels were determined. White blood cell count, neutrophil counts and functions were determined. Peripheral blood cell counts, neutrophil phagocytosis index were decreased but neutrophil adhesivity index was not different in diabetes-induced groups. G-CSF administration improved netrophil counts and function. Macroscopic and microscopic gastric mucosal injury were significantly greater in control and only diabetes group compared with G-CSF pretreated group (p < 0.05). The tissue malondialdehyde and glutathione levels were significantly decreased in G-CSF-administrated diabetic group compared to untreated diabetics (p < 0.001). Finally, G-CSF has been shown to cause neutrophilia and improve neutrophil phagocytosis in diabetic. G-CSF may be cytoprotective for gastric mucosa in diabetes mellitus-induced rats.

VCAM-1-induced inwardly rectifying K(+) current enhances Ca(2+) entry in human THP-1 monocytes

Hyperpolarization in human leukemia THP-1 monocytes adherent to vascular cell adhesion molecule (VCAM)-1 is due to an induction of inwardly rectifying K(+) currents (I(ir)) (Colden-Stanfield M and Gallin EK, Am J Physiol Cell Physiol 275: C267-C277, 1998). We determined whether the VCAM-1-induced hyperpolarization is sufficient to augment the increase in intracellular free calcium ([Ca(2+)](i)) produced by Ca(2+) store depletion with thapsigargin (TG) and readdition of external CaCl(2) in fura 2-loaded THP-1 monocytes. Whereas there was a 2.1-fold increase in [Ca(2+)](i) in monocytes bound to glass for 5 h in response to TG and CaCl(2) addition, adherence to VCAM-1 produced a 5-fold increase in [Ca(2+)](i). Depolarization of monocytes adherent to VCAM-1 by I(ir) blockade or exposure to high [K(+)] abolished the enhancement of the peak [Ca(2+)](i) response. In monocytes bound to glass, hyperpolarization of the membrane potential with valinomycin, a K(+) ionophore, to the level of hyperpolarization seen in cells adherent to VCAM-1 produced similar changes in peak [Ca(2+)](i). Adherence of monocytes to E-selectin produced a similar peak [Ca(2+)](i) to cells bound to glass. Thus monocyte adherence to the physiological substrate VCAM-1 produces a hyperpolarization that is sufficient to enhance Ca(2+) entry and may impact Ca(2+)-dependent monocyte function.

G-proteins in kidneys of spontaneously hypertensive rats

G(s alpha)-, total G(i alpha)- and G(q/11alpha)-protein concentrations were investigated by quantitative immunoblotting in membranes of total kidney, renal cortex and medulla as well as in cortical tubules and glomeruli of Spontaneously Hypertensive Rats (SHR) and normotensive Wistar Kyoto rats (WKY), aged 5 weeks, 3 or 8 months. We found that total kidney of 5 week old SHR possess less G(s alpha)-, G(i alpha)- and G(q/11alpha)-proteins than controls. For G(s alpha)-proteins, differences found in total kidney were mirrored both in cortex (tubules and glomeruli) and in medulla. Decreased G(i alpha)-concentrations were accompanied by lower tubular but higher glomerular levels, while medullar levels were also increased. Decreased G(q/11alpha)-concentrations were reflected in decreased glomerular and medullary concentrations. Kidneys of 3 month old SHR and WKY possessed similar concentrations of all G(alpha)-species. In 8 month old SHR similar G(i alpha)-, but decreased G(s alpha)-and G(q/11alpha)-concentrations were observed. The G(s alpha)-decrease was reflected in cortex and medulla, the G(q/11alpha)-decrease in the medulla. We conclude that the main strain-related differences in G(alpha)-concentrations are seen in prehypertensive SHR.

Impaired prostaglandin E(2)/prostaglandin I(2) receptor-G(s) protein interactions in isolated renal resistance arterioles of spontaneously hypertensive rats

The protective effect of vasodilator agents linked to the cAMP pathway is less effective for buffering the vasoconstrictor effect of angiotensin II in young animals with genetic hypertension. To determine the underlying cellular mechanism, experiments were performed on freshly isolated preglomerular resistance arterioles obtained from kidneys of 7-week-old spontaneously hypertensive rats (SHR) and normotensive Wistar-Kyoto rats (WKY). Specific high-affinity saturable binding of (3)H-prostaglandin (PG) E(2) revealed 1 receptor class in renal microvessels; PGE(2) receptor density was similar in SHR and WKY (106 versus 115 fmol/mg; P>0.8), as was receptor affinity (3.6 versus 3.5 nmol/L; P>0.7). Basal cAMP activity was similar in renal arterioles from SHR and WKY. A major finding was that PGE(2), PGI(2), and isoproterenol produced weaker stimulation of cAMP formation in arteriolar cells of SHR (P<0.02). In contrast, GTPgammas and forskolin stimulated cAMP generation to a similar degree in both rat strains, which suggests normal adenylate cyclase activity in hypertension-prone SHR. Immunoblots revealed the presence of 3 classes of G proteins (G(s), G(i), and G(q)) in preglomerular arterioles. The relative amounts of discernible G-protein alpha-subunits in renal resistance vessels did not differ between SHR and WKY. These results extend previous in vivo studies of abnormal renal vascular reactivity in SHR and more directly localize defective coupling of the prostaglandin and beta-adrenergic receptors to a stimulatory G protein and cAMP production in freshly isolated preglomerular arteriolar cells of young SHR. This dysfunction may be due to an abnormal interaction between prostaglandin receptors and G(s) protein that leads to inefficient coupling of initiating steps in the cAMP-protein kinase A cascade during the development of hypertension.

Metoprolol prevents ischemia-reperfusion injury by reducing lipid peroxidation

Myocardial ischemia and reperfusion result in endothelial and ventricular dysfunction. Beta-blockers protect the myocytes from injury by acting as anti-ischemia agents. These anti-ischemic effects of the beta-blockers are due not only to their negative inotropic/chronotropic effects but also to a lipid peroxidation reducing mechanism. Thus, beta-blockers enhance myocardial recovery. In the present study 20 isolated guinea-pig hearts were perfused with Krebs-Henseleit buffer (KHB) using a Langendorff apparatus. The animals were allocated into 2 groups. In the study group (Group I), metoprolol, as the beta-blocker agent, was added into the KHB and in the control group (Group II) perfusion was performed without metoprolol. The percentage change (%change) of heart rate, developed pressure and dP/dtmax; malondialdehyde (MDA) and glutathione (GSH) levels of the perfusate and heart tissue were obtained as data. The %change of heart rate was 70.5+/-9.2 in the study group and 87.3+/-8.2 in the control (p = 0.003). The %change of developed pressure was 68.7+/-14.4 and 55.9+/-8.6 in the study group and control group, respectively (p = 0.04). The % change of dP/dt was 63.3+/-10.0 in the study group and 54.4+/-5.3 in the control group (p = 0.01). The tissue MDA level was 31.0+/-5.5 nmol/g tissue in the study group and 53.5+/-4.2 nmol/g tissue in the control group (p = 0.0002). The tissue GSH levels were 1.08+/-0.20 and 0.80+/-0.07 (mol/g tissue) in Groups I and II, respectively (p = 0.001). The levels of the perfusate MDA decreased and the levels of the perfusate GSH increased significantly in the metoprolol group in the postreperfusion period in comparison with the preischemia term (p = 0.003 and p = 0.03, respectively). Metoprolol reduces ischemic injury via prevention of lipid peroxidation and reduces the myocardial energy demand by decreasing the heart rate.

Pertussis toxin-sensitive G-proteins and regulation of blood pressure in the spontaneously hypertensive rat

1. Increased Gi-protein-mediated receptor-effector coupling in the vasculature of the spontaneously hypertensive rat (SHR) has been proposed as a contributing factor in the maintenance of elevated blood pressure. If increased Gi-protein-mediated activity plays an important role in hypertension in SHR, then inhibition of Gi-proteins by pertussis toxin would be expected to decrease blood pressure in this genetic hypertensive model. To address this hypothesis, studies were undertaken comparing the cardiovascular effects of pertussis toxin in SHR and normotensive Wistar-Kyoto (WKY) rats. 2. Spontaneously hypertensive and WKY rats were instrumented with radiotelemetry devices and blood pressure measurements were recorded in conscious rats. Following a single injection of pertussis toxin (10 micrograms/kg, i.v.), mean arterial blood pressure fell from 161 +/- 3 to 146 +/- 1 mmHg in the SHR and the effect was sustained for more than 2 weeks. In contrast, 10 micrograms/kg, i.v., pertussis toxin produced no significant effect on blood pressure in WKY rats (103 +/- 4 vs 101 +/- 5 mmHg). 3. In a separate study, SHR and WKY rats were administered 30 micrograms/kg, i.v., pertussis toxin or 150 microL/kg, i.v., saline and, 3-5 days later, rats were anaesthetized and instrumented to permit measurement of blood pressure and renal function. At this higher dose, pertussis toxin reduced blood pressure in both strains of rat, although the effect was markedly greater in SHR (approximately 40 mmHg decrease) compared with WKY rats (approximately 15 mmHg decrease). In SHR, pertussis toxin increased renal blood flow (from 5.7 +/- 0.3 to 7.5 +/- 0.8 mL/min per g kidney) and decreased renal vascular resistance (from 31 +/- 2 to 19 +/- 2 mmHg/mL per min per g kidney). In WKY rats, pertussis toxin had no significant effect on renal parameters. 4. Results from these studies indicate that a pertussis toxin-sensitive Gi-protein-mediated pathway contributes to the maintenance of hypertension and elevated renal vascular tone in the SHR.

Acellular hemoglobin-mediated oxidative stress toward endothelium: a role for ferryl iron

We tested the hypothesis that chemical modifications used to produce stable, oxygen-carrying, Hb-based blood substitutes can induce cytotoxicity in endothelial cells in culture because of altered redox activity. We examined the interaction of hydrogen peroxide with nonmodified hemoglobin (HbA0) and two chemically modified hemoglobins, alpha-cross-linked hemoglobin (alpha-DBBF) and its polymerized form (poly-alpha-DBBF). Hydrogen peroxide-induced cell death (as assessed by lactate dehydrogenase release) in bovine aortic endothelial cells (BAEC) was completely inhibited by all three hemoglobin preparations, consistent with their known pseudoperoxidase activity [hemoglobin consumes peroxide as it cycles between ferric (Fe3+) and ferryl (Fe4+) hemes]. However, reaction of the modified hemoglobins, but not HbA0, with hydrogen peroxide induced apoptotic cell death (as assessed by morphological changes and DNA fragmentation) that correlated with the formation of a long-lived ferrylhemoglobin. A preparation of ferryl-alpha-DBBF free of residual peroxide rapidly induced morphological changes and DNA fragmentation in BAEC, indicative of apoptotic cell death. Redox cycling of chemically modified hemoglobins by peroxide yielded a persistent ferryl iron that was cytotoxic to endothelial cells.

Stretch-activated cation channel in human umbilical vein endothelium in normal pregnancy and in preeclampsia

OBJECTIVE

To determine whether stretch-activated cation channels (SAC) are present in intact human umbilical vein endothelium (HUVE) and in an endothelial cell line (EA.hy) and whether they act as endothelial mechanosensors, and to determine whether endothelial SAC in HUVE from women with pregnancies complicated by preeclampsia undergo functional changes compared with those in HUVE from women with normotensive pregnancies.

METHODS AND RESULTS

By use of the patch-clamp technique we identified a SAC in intact HUVE and in an endothelial cell line. The SAC had mean conductances of 29+/-5 pS (n = 38) for K+ and 12+/-2 pS (n = 4) for Ca2+. Administration of 50 micromol/I gadolinium, a blocker of mechanosensitive ion channels, completely blocked activity of this channel. We found from single-channel recordings that influx of Ca2+ through SAC directly activated high-conductance Ca2+-dependent potassium channels, proving that a significant influx of Ca2+ through SAC occurs at physiologic concentrations of Ca2+. In a comparative study, apparent channel density of SAC (percentage of patches with SAC activity) in HUVE from women with pregnancies complicated by preeclampsia (36.2 +/- 4.3%) was twofold higher than that in HUVE from women with normal pregnancies (17.9+/-2.9%, P< 0.01). Channel conductance and sensitivity to stretching of SAC were not altered by preeclampsia.

CONCLUSIONS

Since SAC are capable of acting as endothelial mechanosensors, the greater than normal density of SAC associated with preeclampsia might reflect an alteration of mechanotransduction.

Renal substance P-containing neurons and substance P receptors impaired in hypertension

In normotensive rats, increased renal pelvic pressure stimulates the release of prostaglandin E and substance P, which in turn leads to an increase in afferent renal nerve activity (ARNA) and a contralateral natriuresis, a contralateral inhibitory renorenal reflex. In spontaneously hypertensive rats (SHR), increasing renal pelvic pressure failed to increase afferent renal nerve activity. The inhibitory nature of renorenal reflexes indicates that impaired renorenal reflexes could contribute to increased sodium retention in SHR. Phorbol esters, known to activate protein kinase C, increase afferent renal nerve activity in Wistar-Kyoto rats (WKY) but not in SHR. We examined the mechanisms involved in the impaired responses to renal sensory receptor activation in SHR. The phorbol ester 4beta-phorbol 12,13-dibutyrate increased renal pelvic protein kinase C activity similarly in SHR and WKY. Increasing renal pelvic pressure increased afferent renal nerve activity in WKY (27+/-2%) but not in SHR. Renal pelvic release of prostaglandin E increased similarly in WKY and SHR, from 0.8+/-0.1 to 2.0+/-0.4 ng/min and 0.7+/-0.1 to 1.4+/-0.2 ng/min. Renal pelvic release of substance P was greater (P<.01) in WKY, from 16.3+/-3.8 to 41.8+/-7.4 pg/min, than in SHR, from 9.9+/-1.7 to 17.0+/-3.2 pg/min. In WKY, renal pelvic administration of substance P at 0.8, 4, and 20 microg/mL increased ARNA 382+/-69, 750+/-233, and 783+/-124% second (area under the curve of afferent renal nerve activity versus time). In SHR, substance P at 0.8 to 20 microg/mL failed to increase ARNA. These findings demonstrate that the impaired afferent renal nerve activity response to increased renal pelvic pressure is related to decreased release of substance P and/or impaired activation of substance P receptors.

Endothelial cells from diverse tissues exhibit differences in growth and morphology

An increased recognition of the role of endothelial cells in disease and the development of methods for endothelial cell culture has led to an upsurge in in vitro studies of endothelial cell function. However, the cells most often used for these studies do not reflect the in vivo heterogeneity of endothelial cells. To assess intrinsic differences between large and small vessel endothelial cells from different tissues, primary cultures of endothelial cells from capillaries (brain, lung, and adipose tissue) and a large vessel (aorta) of sheep were isolated, purified by fluorescence-activated cell sorting of acetylated low density lipoprotein (DiI-Ac-LDL) labeled cells, and characterized by phase contrast and ultrastructural morphology, expression of von Willebrand factor, and lack of expression of cytokeratin, smooth muscle actin, and glial fibrillary acidic protein (GFAP). Although all endothelial cells were cultured in the same media, only the brain microvascular endothelial cells demonstrated tight junctions by electron microscopy. Only the large vessel (aortic) endothelial cells contained Weibel-Palade bodies. Expression of von Willebrand factor decreased with passage of cells, but uptake of DiI-Ac-LDL was consistently positive regardless of culture conditions or passage number. These studies demonstrate that the unique ultrastructural characteristics of microvascular and macrovascular endothelial cells are intrinsic to the cells themselves and are not determined by differential culture conditions. This system allows the study of pathologic processes that affect endothelial cells of certain target organs selectively and should more accurately represent the response of tissue-specific endothelial cells in inflammatory processes.

Calcium signaling mechanisms in renal vascular responses to vasopressin in genetic hypertension

Previous blood flow studies demonstrated that arginine vasopressin (AVP) produces exaggerated renal vasoconstriction in young spontaneously hypertensive rats (SHR) compared with Wistar-Kyoto control rats (WKY). The purpose of the present study was to determine the role of postreceptor calcium signaling pathways in AVP-induced renal vasoconstriction in vivo. Renal blood flow (RBF) was measured by electromagnetic flowmetry in anesthetized, water-loaded, 8-week-old WKY and SHR pretreated with indomethacin to avoid interactions with prostaglandins. AVP was injected into the renal artery to produce a transient 25% to 30% decrease in RBF without affecting arterial pressure. To achieve similar control levels of vasoconstriction, SHR received a lower dose (2 versus 5 ng). Coadministration of nifedipine with AVP produced dose-dependent inhibition of the AVP-induced renal vasoconstriction. Nifedipine exerted maximum inhibition by blocking 30% to 35% of the peak AVP response, indicating the involvement of dihydropyridine-sensitive voltage-dependent calcium channels. To evaluate intracellular calcium mobilization, 8-(N,N-diethylamino)octyl-3,4,5-trimethoxybenzoate (TMB-8) or heparin was coadministered with AVP. Each agent produced a dose-dependent inhibition of up to 65% of the maximum blood flow change produced by AVP. The degrees of inhibition produced by maximum effective doses of nifedipine and TMB-8 were additive; the combination blocked up to 85% of the response to AVP. These observations indicate that about one third of the AVP-induced constriction of renal resistance vessels is mediated by voltage-dependent L-type calcium channels responsive to the dihydropyridine nifedipine. Approximately two thirds of the change in vascular tone is due to inositol 1,4,5-trisphosphate-mediated calcium mobilization from intracellular sources sensitive to TMB-8 and heparin. The results suggest that the exaggerated renal vascular reactivity to AVP challenge in SHR is probably not due to a strain difference in postreceptor calcium signal transduction. After AVP receptor stimulation, calcium mobilization and calcium entry signaling pathways participate to similar degrees in WKY and SHR.

Ion channels in vascular endothelium

The functional impact of ion channels in vascular endothelial cells (ECs) is still a matter of controversy. This review describes different types of ion channels in ECs and their role in electrogenesis, Ca2+ signaling, vessel permeability, cell-cell communication, mechano-sensor functions, and pH and volume regulation. One major function of ion channels in ECs is the control of Ca2+ influx either by a direct modulation of the Ca2+ influx pathway or by indirect modulation of K+ and Cl- channels, thereby clamping the membrane at a sufficiently negative potential to provide the necessary driving force for a sustained Ca2+ influx. We discuss various mechanisms of Ca2+ influx stimulation: those that activate nonselective, Ca(2+)-permeable cation channels or those that activate Ca(2+)-selective channels, exclusively or partially operated by the filling state of intracellular Ca2+ stores. We also describe the role of various Ca(2+)- and shear stress-activated K+ channels and different types of Cl- channels for the regulation of the membrane potential.

Effects of indomethacin and iloprost on contraction of the afferent arterioles by endothelin-1 in juxtamedullary nephron preparations from normotensive Wistar-Kyoto and spontaneously hypertensive rats

The contractile effects of endothelin-1 on the afferent arterioles of normotensive Wistar-Kyoto (WKY) and spontaneously hypertensive rats (SHR) and the modulation of these responses by cyclooxygenase blockade or by the prostacyclin analog iloprost were investigated. For this, the preglomerular vasculature was visualized by using the juxtamedullary nephron preparation. Endothelin-1 (100 pM-1 microM) induced concentration-dependent reduction of afferent diameters either in WKY and SHR kidneys, which were inhibited by 1 microM nifedipine, indicating its dependence on extracellular calcium. After incubation with 20 microM indomethacin, the endothelin-1-induced contractions were potentiated in WKY but abolished in SHR vessels. These results could be explained if endothelin-1 is releasing vasodilator prostanoids in WKY, whereas in SHR preparations, vasoconstrictor prostanoids predominate. The prostacyclin analog iloprost (1 nM-1 microM) did not modify basal diameters of the WKY afferent arterioles, whereas a weak vasodilatatory effect was observed in the SHR afferent vasculature. Both in WKY and SHR preparations, iloprost (10 nM-1 microM) abolished the afferent contractility by endothelin-1, this effect being more prominent in SHR. We conclude that a defective production of vasodilator prostanoids or an enhanced release of vasoconstrictor cyclooxygenase derivatives may determine the renovascular effects of endothelins in SHR kidneys.

Bradykinin and protein kinase C activation fail to stimulate renal sensory neurons in hypertensive rats

In normotensive rats, renal sensory receptor activation by increased ureteral pressure results in increased ipsilateral afferent renal nerve activity, decreased contralateral efferent renal nerve activity, and contralateral diuresis and natriuresis, a contralateral inhibitory renorenal reflex response. In spontaneously hypertensive rats (SHR), increasing ureteral pressure fails to increase afferent renal nerve activity. The nature of the inhibitory renorenal reflexes indicates that an impairment of the renorenal reflexes would contribute to the increased efferent renal nerve activity in SHR. We therefore examined whether there was a general decrease in the responsiveness of renal sensory receptors in SHR by comparing the afferent renal nerve activity responses to bradykinin in SHR and Wistar-Kyoto rats (WKY). In WKY, renal pelvic perfusion with bradykinin at 4, 19, 95, and 475 micromol/L increased afferent renal nerve activity by 1066 +/- 704, 2127 +/- 1121, 3517 +/- 1225, and 4476 +/- 1631% x second (area under the curve of afferent renal nerve activity versus time). In SHR, bradykinin at 4 to 95 micromol/L failed to increase afferent renal nerve activity. Bradykinin at 475 micromol/L increased afferent renal nerve activity in only 6 of 10 SHR. In WKY, renal pelvic perfusion with the phorbol ester 4beta-phorbol 12,13-dibutyrate, known to activate protein kinase C, resulted in a peak afferent renal nerve activity response of 24 +/- 4%. However, 4beta-phorbol 12,13-dibutyrate failed to increase afferent renal nerve activity in SHR. These findings demonstrate decreased responsiveness of renal pelvic sensory receptors to bradykinin in SHR. The impaired afferent renal nerve activity responses to bradykinin in SHR may be due to a lack of protein kinase C activation or a defect in the intracellular signaling mechanisms distal to protein kinase C activation.

Effects of lisinopril on the structure of renal arterioles

We investigated the effect of long-term administration of the angiotensin-converting enzyme inhibitor lisinopril on renal arterioles in spontaneously hypertensive rats (SHR) and Wistar-Kyoto rats (WKY) using a morphometric method and vascular cast technique. Rats were treated with lisinopril beginning at 4 weeks of age. At 15 weeks of age, the kidney vessels were fixed when maximally relaxed. Resin was perfused into the right kidney to make a cast of the renal vasculature. The opposite kidney was used for the morphometric study to evaluate structural changes of the vascular wall. The vascular cast study demonstrated a significant reduction in the lumen diameter of the afferent but not the efferent arterioles in SHR compared with those in WKY. In lisinopril-treated rats, the afferent arteriolar lumen diameters were significantly larger than those of the respective control groups in both strains. However, treatment did not affect the lumen diameter of efferent arterioles in either strain. The morphometric study revealed that the cross-sectional area of afferent arteriolar media was significantly smaller in SHR than WKY, suggesting that the impaired growth of the afferent arteriolar media was involved in the narrowed afferent arteriolar lumen in SHR. The presence of significantly smaller media-lumen ratio, greater media cross-sectional area, and larger internal as well as external diameters of the afferent arterioles in treated SHR than in untreated rats suggested that lisinopril treatment normalizes the structure of the afferent arterioles in SHR by vascular reverse remodeling and by inducing media growth.

Classification of ion channels in the luminal and abluminal membranes of guinea-pig endocardial endothelial cells

1. The ion channels on both the luminal and abluminal membranes of endocardial endothelial (EE) cells were separately recorded using the patch clamp technique in the guinea-pig heart. 2. The major population consisted of two types of non-selective cation channels, which showed open probabilities of 0.21 and 0.33 at the resting potential, and conductances of 36 and 11 pS, respectively. 3. The next major class was Cl- channels with an ohmic conductance of 409 pS. The channel was quiescent in the cell-attached mode but was activated by strong depolarization after excising the patch membrane. 4. The channels activated by intracellular Ca2+ were mainly K+ channels showing a 34 pS slope conductance and, less frequently, Ca(2+)-dependent K+ channels having a large conductance (210 pS). The inward rectifier K+ channel (32 pS) was also observed. 5. The non-selective cation channels were recorded on the luminal membrane, but scarcely on the abluminal membrane, suggesting an active transport of K+ and Na+ across the endocardium. 6. The resting membrane conductance of the EE cells may be provided mostly by non-selective cation channels and 34 pS Ca(2+)-dependent K+ channels.

Hyperpolarization induced by vasoactive substances in intact guinea-pig endocardial endothelial cells

1. The responses of guinea-pig endocardial endothelial (EE) cells to various vasoactive substances were investigated in either the small tissue preparation or freshly isolated cells using the patch clamp technique. 2. The mean resting potential of the EE cell was -44 mV in the small tissue preparation, and applications of ATP, ADP, AMP, adenosine, histamine and substance P induced transient hyperpolarizations of -22, -21, -9, -10, -23 and -15 mV, respectively. The membrane potential of EE cells failed to respond to acetylcholine, bradykinin, thrombin, atrial natriuretic peptide, vasopressin and serotonin. 3. The whole-cell voltage clamp of dissociated cells revealed a transient increase of K+ conductance underlying the ATP and histamine responses. The agonist-induced current showed no time-dependent change during voltage steps. The response was showed no time-dependent change during voltage steps. The response was prevented by adding 10 mM EGTA to the pipette solution. 4. In the cell-attached single channel recordings, ATP induced transient K+ channel activities having a slope conductance of 34 pS. In inside-out patches, similar K+ channels were activated by applying Ca2+ of more than 0.1 microM. 5. These findings are consistent with the idea that the Ca(2+)-dependent K+ channel is involved in the hyperpolarizing response of EE cells, as described in vascular endothelial cells.

Regulation of blood-brain barrier endothelial cells by nitric oxide

Nitric oxide (NO) synthesized by vascular endothelial cells is a potent vasodilator substance. The actions of NO extend well beyond its vasodilatory properties, and increasingly, NO has been recognized as an important signal for intercellular and intracellular communication. Recently, NO has been implicated in the regulation of vascular and blood-brain barrier permeability. NO has also been shown to modulate ion channels in excitable cells, thus affecting neuronal firing. We report the results of patch-clamp experiments that show a modulatory action of NO as well as cGMP and cAMP on a hyperpolarization-activated current (Iha) carried by both Na+ and K+ ions in blood-brain barrier endothelial cells. Iha was recorded in cells dialyzed with 0.2 mmol/L GTP-gamma-S to inhibit a large inwardly rectifying potassium current. This ionic current and its modulation by NO may play a role in the regulation of the transport of ions, nutrients, and other molecules to the brain and serve as an integral part of the blood-brain barrier. The modulation of Iha by a cyclic guanosine nucleotide may also explain previous reports suggesting a role for NO in the regulation of blood-brain barrier function.

Ca2+ influx through stretch-activated cation channels activates maxi K+ channels in porcine endocardial endothelium

The endocardial endothelium is an important modulator of myocardial function. The present study demonstrates the existence of a stretch-activated Ca(2+)-permeable cation channel and of a Ca(2+)-activated K+ channel in the endocardial endothelium of the porcine right atrium. The stretch-activated channel is permeable for K+, Na+, Ca2+, and Ba2+, with mean conductances of approximately 32 pS for the monovalent cations and approximately 13 pS for divalent cations. The Ca(2+)-activated K+ channel has a mean conductance of 192 pS in symmetrical KCl. solution. Channel activity is strongly dependent on membrane potential and the cytosolic Ca2+ concentration. Half-maximal activation occurs at a cytosolic Ca2+ concentration of approximately 5 microM. The influx of Ca2+ through the stretch-activated channel is sufficient to activate the Ca(2+)-activated K+ channel in cell-attached patches. Upon activation of the stretch-activated channel, the cytosolic Ca2+ concentration increases, at least locally, to values of approximately 0.5 microM, as deduced from the open probability of the Ca(2+)-dependent K+ channel that was activated simultaneously. The stretch-activated channels are capable of inducing an intracellular Ca2+ signal and may have a role as mechanosensors in the atrial endothelium, possibly activated by atrial overload.

Modulation by histamine of an inwardly rectifying potassium channel in human endothelial cells

1. Whole-cell and single-channel currents were recorded together with intracellular Ca2+ in voltage clamped, single endothelial cells isolated from human umbilical vein. 2. The major current component under resting conditions in the whole-cell configuration was a strongly inwardly rectifying potassium current. 3. This current is due to activation of a K+ channel with an inward conductance of 29 +/- 3 pS (n = 7) with symmetrical 140 mM K+ on both sides of the membrane. This channel could be measured both in the cell-attached and in the inside-out configuration. At potentials below -110 mV both whole-cell and averaged single-channel currents showed a fast inactivation. 4. During stimulation of endothelial cells with histamine, whole-cell K+ currents initially increased but then substantially declined, despite the sustained increase in intracellular Ca2+ concentration ([Ca2+]i). 5. The blockade of the inwardly rectifying K+ channel by histamine could not be observed in cell-attached patches if histamine was added to the bath. 6. It is concluded that endothelial cells possess K+ channels that are directly inhibited by agonists, such as histamine. Blocking these channels may depolarize the cell membrane and thereby reduce the driving force for Ca2+ influx.